The present invention relates to a novel human gene encoding a polypeptide which is a member of the erythroid differentiation factor family. More specifically, the present invention relates to a polynucleotide encoding a novel human polypeptide named Bone Marrow-Specific Protein, or xe2x80x9cBMSP.xe2x80x9d This invention also relates to BMSP polypeptides, as well as vectors, host cells, antibodies directed to BMSP polypeptides, and the recombinant methods for producing the same. Also provided are diagnostic methods for detecting disorders related to the immune system, and therapeutic methods for treating such disorders. The invention further relates to screening methods for identifying agonists and antagonists of BMSP activity.
Erythroid cells are critically important for embryonic development. During embryonic development, two distinct forms of erythropoiesis occur. First, a xe2x80x98primitivexe2x80x99 form consists of nucleated erythroblasts that differentiate within the blood vessels of the extraembryonic yolk sac. Second, a xe2x80x98definitivexe2x80x99 form consists of anucleate erythrocytes that differentiate within the liver and third trimester bone marrow of the fetus. During the third trimester the fetus grows rapidly and the production of red cells is approximately 3-5 times that of adult steady state levels. Erythropoiesis occurs first in the yolk sac, subsequently in the liver, and then the bone marrow and, in rodents, the spleen during development. Birth brings dramatic changes in oxygenation and erythropoietin production that result in a tenfold drop in red cell production and in a transient xe2x80x98physiologicxe2x80x99 anemia. Even in the adult, vestiges of fetal erythropoiesis are evident during transient states of accelerated erythroid expansion. The precise complement of molecular factors and signals which mediate the processes involved in erythropoiesis and developmental progression of other immune cells both during fetal development and after birth is not clearly defined.
Myeloid cells arise from a common stem cell progenitor whose development is regulated by stimulatory and inhibitory growth factors. Pluripotential hematopoietic stem cells are most influenced by cytokines and growth factors including, but not limited to, IL-3, GM-CSF, and stem cell factor while committed progenitor cells are regulated by variable concentrations of cytokines and growth factors including, for example, GM-CSF, G-CSF, M-CSF, IL-5, Epo, and Tpo. Both dysplastic and neoplastic conditions can thus be traced to a common origin. Dysplastic changes may signal early neoplastic changes with cases progressing to acute leukemia. Myelodysplastic syndrome (MDS) is associated with anemia or multiple cytopenias, normal to hypercellular bone marrow, ineffective hematopoiesis, and less than 30% blast cells of all nucleated cells in the bone marrow. Chronic myeloid leukemias also have less than 30% blast cells of all nucleated cells in the bone marrow and are distinguished from MDS by elevated cell counts of one or more cell lines with mature forms predominating. Acute myeloid leukemias, often the end result of all myeloproliferative disorders, are recognized by equal or greater 30% blast cells of all nucleated cells in the bone marrow. In fact, although many myelogenic regulatory factors have been at least preliminarily characterized, it is clear that a number of factors have not yet been identified.
Thus, there is a need for polypeptides that are involved in bone growth defects and immune functions, such as defects in stem cell growth and/or blood cell differentiation, since disturbances of such regulation may be involved in disorders relating to immune system. Therefore, there is a need for identification and characterization of such human polypeptides which can play a role in detecting, preventing, ameliorating or correcting such disorders.
The present invention relates to a novel polynucleotide and the encoded polypeptide of BMSP. Moreover, the present invention relates to vectors, host cells, antibodies, and recombinant methods for producing the polypeptides and polynucleotides. Also provided are diagnostic methods for detecting disorders relates to the polypeptides, and therapeutic methods for treating such disorders. The invention further relates to screening methods for identifying binding partners of BMSP.
FIG. 1 shows the nucleotide sequence (SEQ ID NO:1) and the deduced amino acid sequence (SEQ ID NO:2) of BMSP. Two potential Casein Kinase II (CK2) phosphorylation sites are marked in FIG. 1 with bolded serine (S) or threonine (T) symbols in the BMSP amino acid sequence and also marked with an asterisk (*) above the first nucleotide encoding the appropriate serine and threonine residues in the BMSP nucleotide sequence. The first potential CK2 phosphorylation sequence is found at the following location in the BMSP amino acid sequence: S-33 through D-36 (S-33, E-34, E-35, and D-36). The second potential CK2 phosphorylation sequence is found at the following location in the BMSP amino acid sequence: T-39 through E42 (T-39, V-40, V-41, and E-42).
Regions of high identity between BMSP and the closely related Mus musculus erythroid differentiation related factor (MEDRF) sequence (SEQ ID NO:3) are delineated in FIG. 1 with a double underline. These regions are not limiting and are labeled as Conserved Domain (CD)-I, CD-II, CD-III, CD-IV, CD-V, CD-VI, and CD-VII in FIG. 1.
FIG. 2 shows the regions of identity between the amino acid sequence of the BMSP protein and the translation product of the Mus musculus erythroid differentiation related factor (MEDRF) gene (SEQ ID NO:3; ATCC Accession No. AF060220), determined by BLAST analysis. By examining the regions of amino acids which are identical or similar between BMSP and MEDRF, the skilled artisan can readily identify conserved domains between the two polypeptides. These conserved domains are preferred embodiments of the present invention.
FIG. 3 shows an analysis of the BMSP amino acid sequence. Alpha, beta, turn and coil regions; hydrophilicity and hydrophobicity; amphipathic regions; flexible regions; antigenic index and surface probability are shown, and all were generated using the default settings. In the xe2x80x9cAntigenic Index or Jameson-Wolfxe2x80x9d graph, the positive peaks indicate locations of the highly antigenic regions of the BMSP protein, i.e., regions from which epitope-bearing peptides of the invention can be obtained. The domains defined by these graphs are contemplated by the present invention.
The data presented in FIG. 3 is also represented in tabular form in Table I. The columns in Table I are labeled with the headings xe2x80x9cResxe2x80x9d, xe2x80x9cPositionxe2x80x9d, and Roman Numerals I-XIV. The column headings refer to the following features of the amino acid sequence presented in FIG. 3 and Table I: xe2x80x9cResxe2x80x9d: amino acid residue of SEQ ID NO:2 and FIG. 1; xe2x80x9cPositionxe2x80x9d: position of the corresponding residue within SEQ ID NO:2 and FIG. 1; I: Alpha, Regionsxe2x80x94Garnier-Robson; II: Alpha, Regionsxe2x80x94Chou-Fasman; III: Beta, Regionsxe2x80x94Garnier-Robson; IV: Beta, Regionsxe2x80x94Chou-Fasman; V: Turn, Regionsxe2x80x94Garnier-Robson; VI: Turn, Regionsxe2x80x94Chou-Fasman; VII: Coil, Regionsxe2x80x94Garner-Robson; VIII: Hydrophilicity Plotxe2x80x94Kyte-Doolittle; IX: Hydrophobicity Plotxe2x80x94Hopp-Woods; X: Alpha, Amphipathic Regionsxe2x80x94Eisenberg; XI: Beta, Amphipathic Regionsxe2x80x94Eisenberg; XII: Flexible Regionsxe2x80x94Karplus-Schulz; XIII: Antigenic Indexxe2x80x94Jameson-Wolf; and XIV: Surface Probability Plotxe2x80x94Emini.